Method of making multicore electrical conductors



Jan. 16, 1951 E. c. LEE 2,538,019

METHOD OF MAKING MULTICORE ELECTRICAL CONDUCTORS Filed Jan. 7, 1947Inventor [aw/Al (HA/H E: LEE

Patented Jan. 16,1951

METHOD OF MAKING MULTICORE ELECTRICAL CONDUCT'ORS' Edwin Charles Lee,London, England, assignor to International Standard ElectricCorporation, New York, N. Y., a corporation of Delaware ApplicationJanuary 7, 1947, Serial No. 720,562 'In Great Britain October 29, 1945Section 1, Public Law 690, August 8, 1946 Patent expires October 29,1965 1 Claim. (Cl. 154 2.24)

This invention relates to electric cables and more particularly tomulti-core electric power cables.

Paper, whether um'mprcgnated or impregnated with an insulating compoundis a normal form of insulation in electric cables. The usual method ofapplying this form of insulation is to lap the required numbers ofpapers in the form of narrow strips around the conductors to formseparate cores. Additional layers of paper may then be applied aroundthe cores after they have been laid up in cable form. For high voltagecables,'say 11,000 volts and over, the papers must be applied withprecision to avoid the formation of spaces within the dielectric, butfor lower voltages the thickness of insulation is designed formechanical rather than electrical considerations.

The' application of the paper insulation represents an appreciableproportion of the total cost of making the cable. In a four core cable,for example, there are five distinct lapping operations necessitatingfive different passes through the lapping machine. Furthermore theprocess is comparatively slow owing to the narrow widths of the papertapes.

An object of the present invention is to cheapen the process of making apower cable by eliminating the lapping operations on the individualcores. 7

According to one feature of the present invention we provide amulti-core electric power cable in which the several cores are insulatedfrom one another by means of a member extending along the length of thecable the cross section of which comprises a plurality of arms radiatingfrom a centre, the separate conductor cores being laid between the arms.

The above-mentioned member may be formed so that the portions whosecross sections constitute the arms are helical so that the conductorcores are laid in helices, as must be the case if 2 Preferably also theflexible arms are 'made of suflicient length to enable them to be foldedaround the separate conductors.

The invention will be better understood from the following descriptionof one embodiment, as applied to a four core cable, taken in conjunctionwith the accompanying drawings in which: Fig. 1 shows a cross section ofan electric power cable in accordance With the invention.

Figs. 2, 3 and 4 show successive steps in the formation of theinsulation of the cable of Fig. 1. Fig. 5 shows the form in which theinsulating member of Figs. 2 to 4 may be stored.

Referring to the drawings, an electric power cable is formed with amember I having four arms radiating from the centre, so as, in the caseof the four core cable illustrated, to have a cruciform cross section.This central member is formed from a plurality of superposed paperstrips in the manner shown in Figs. 2 to 4. Fig. 2 shows in crosssection a plurality of paper strips laid one above the other. The width3 of the strips is sumcient to enable the formation of the arms 2 ofFig. 1. The length at right angles to the plane of the paper may besufiicientto produce a manufacturing length of cable without jointingalthough there is no objection to making a joint by over-lapping thepapers. The

, papers are folded lengthwise as shown in Fig. 3

the cable is to be flexible but preferably the member is of flexiblematerial so that the process of laying up the separate conductors toform the,

included in the laying up of the conductors d to form the cable in whichcase the guides and supply rolls for the paper strips would be attachedto the cable making machine. The paper member shown in Fig. 4 is thenfed along the centre line of the machine and the copper conductors 4guided between the limbs. The portions of the arms 2 extending beyondthe conductors are then folded around the conductors, as shown in Fig. 1by passage through a die. Fillers 5, in the form of extended foldedstrips of paper or jute string, folded into the cross section shown inFig. 1 are guided into position and the assembly passed through a seconddie to form an approximately circular section. The effect of the fillersis to complete the turnover of the extremities of the arms 2 and to fillup the gaps at the extremities of the radial portions of these arms.Finally, on leaving the second die, the outer or belt papers 6 areapplied by the usual rotating head.

During the laying up operation the conductors 4 are twisted according tonormal practice and preferably are pretwisted during the stranding 3 ofthe individual wires, again according to normal practice.

If desired a central filler I may be inserted during the manufacture ofthe cable.

After the application of the belt insulation 6 a lead sheath (not shown)is applied by extrusion in the normal manner.

If desired the central member I after being formed into the shape shownin Fig. 4 may be stored, before being used in the manufacture of thecable, by being flattened into the shape shown in Fig. 5 and coiled on adrum, which drum is then mounted whenrequire'd on the laying up machine.

It is clear that the invention can readily :be applied to themanufacture of a cable of any number of cores.

What is claimed is:

A process for producing a multi-core electric power cable comprising thesteps of superimposing a plurality of insulating paper strips in stackedrelation, folding said stacked strips as a continuous unit intocruciform shape, laying a. plurality of conductors between the arms ofsaid cruciform, folding each arm to completely encircle a conductorcore, inserting a filler at the center from which the arms radiate andinserting peripheral fillers in the openings between the end of each armand the nextadjacentarm.

EDWIN CHARLES LEE.

REFERENCES CITED The following references are of record in the file ofthis patent:

v UNITED STATES PATENTS Number Name Date 71,389,143 Kempton Aug. 30,1921 1,663,878 Emanueli Mar. 27, 1928 2,125,869 Atkinson Aug. 9, 19382,264,439 Guyatt Dec, 2, 1941 FOREIGN PATENTS Number Country Date 22,923Great Britain Aug. 12, 1893 of1892 342,606 Great Britain Feb. 5, 1931

